proper furling construction question

[Hoskald]

Greetings all,

I am new to this and still trying to get my head around some of the construction concepts.  The one that has me baffled is the furling mechanism. What is the proper way to construct the furling part? I've read most of the projects, but this step seems to just be assumed...which leads me to believe it's really simple and that I've just been dense!

Thanks in Advance!

Hos

[Flux]

DanB has explained this well and you should be able to find it somewhere on the board discussion or in the articles on the Otherpower site.

It's basically simple but there are factors that are far from simple and a few traps to fall into. I suspect some never really get it and they are lucky that they don't get big winds.

Others seem able to find things better here perhaps someone can find a link.

Flux

[Walt]

Here is one of Dan's responses to furling.

http://www.fieldlines.com/story/2005/3/9/232440/9997

Hope it helps.

[Hoskald]

Thanks for the link...I think I can build one now, but my problem is I'm not understanding how this works at all.

The way I see it (obviously wrong) is that the tail is always in line with the wind, no matter how fast the wind is blowing, and since there is no information flowing between the rotor and the tail, rotor speed doesn't directly account for the furling. Now does the furling action have something to do with the turbulence behind the rotor?

Still trying to get my head around the why...

Thanks!

Hos

[Ungrounded Lightning Rod]

Hey DanB:

What do you use/recommend for:

 - The turbine axis offset from the yaw axis.

 - The angle of the tail pivot from vertical

 - The angle of the tail pivot assembly from straight back

which have to be known to weld up the head, and:

 - the distance from the tail pivot to the center of the tail vane

 - the area of the tail vane

 - the distance from the tail pivot to the pivoting assembly's

   center of mass times the weight of the pivoting assembly

which can be played with later?

Do you have any formulas?  If not, what did you use on some

typical mills that worked out well?

[Fiddlehead44]

The answer, my friend is blowing in the wind........

   The pivot point of the tail assembly is offset from the generator

blade assembly and also mounted at an angle. Allo of this, along with

the weight of the tail, will keep your blades pointed into the wind.

If the wind picks up speed, the pressure on the blades will try to turn

the blade-gen assembly away from the wind, but the tail weight will

hold it steady. The wind increases and now this tail weight will not

hold it(blades) into the wind. Now the gen. assembly will bend (furl)

sideways and get away from the direct force of the wind. Wind slows down

and the weight of the tail now becomes stronger than the wind and all

straightens out. The tail always stays with the wind ,

but the head assembly does the furling.

    Fiddlehead

[Hoskald]

Fiddlehead,

Thanks! Now I get it!!! It's a combination of the weight of the tail, angle of off-set and the tail AREA!

These combined provide the "speed" at which the head furls...

Somehow I completed spaced on the tail area...that fills in the missing component nicely.

Sometimes I can be as dense as this Oklahoma clay....

[Flux]

Not sure what Dan uses but I suspect it will not be much different from this.

Offset min 4% rotor diameter ( 1/2" per foot of rotor seems a good figure).

Angle from vertical about 20 deg.

Angle from straight back is not critical, I think Dan uses 45 deg, Hugh I think uses 55 deg, it has some effect on the power produced during furling.

Distance from tail pivot to centre of vane is typically blade length ( 1/2 rotor diameter) I like it longer but with plywood vanes it may not furl early enough if you go too far.

I will leave the area to Dan, I always tend to make mine too small and need the tail at a considerable angle to keep things straight into the wind.( maybe 16% of blade swept area is reasonable)

You can only find the tail moment by experiment but plywood tails normally work about right with boom length about 1 blade radius.

Flux